Field of the Invention
The invention relates to a method for expanding a ring, and more particularly to a method for expanding a rectangular section ring to form a non-rectangular section ring.
Description of the Related Art
The rectangular section ring (referring to a ring having a rectangular cross section) or the non-rectangular section ring (referring to a ring having a non-rectangular section) of the high temperature alloy generally has poor dimensional accuracy after being rolled by a ring rolling machine due to the limitations of the rolling process and the rolling device. Only when the ring has an ideal shape and the device presents relatively excellent performance, the dimensional accuracy is approximately between 3% and 5% of the corresponding dimension. Besides, defects including warp, deformation, and even cracking easily occur on the ring as a result of a relatively large stress in subsequent processing operations.
Conventional methods for expanding of a ring are based on the flexible contact between the liquid and an inner circumferential surface of the ring. The methods are only applicable for materials having small deformation resistance and mainly operate to reinforce the ring. However, the methods are neither applicable for materials having large deformation resistance, such as a high temperature alloy, nor applicable for expanding a rectangular section ring into a non-rectangular section ring. Furthermore, the methods are unable to solve the poor dimensional accuracy existing in the prior art.